1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to a brake assembly for a steerable catheter that allows both dynamic locking and swapping between a locked mode of operation and an unlocked mode of operation.
2. Description of Related Art
Medical practitioners frequently use catheters to access internal regions of a patient""s body for a variety of medical procedures. The use of catheters advantageously reduces or eliminates the need for more invasive procedures. Medical catheters may be used to access internal body regions with a fiberoptic scope, light bundles, and/or other surgical instruments or devices, for a variety of diagnosis, treatment and/or material delivery purposes. For example, U.S. Pat. No. 5,658,263 to Dang, et al. discloses a multi-segmented guiding catheter typically utilized for internal vascular access.
Steerable catheters have been developed to provide improved access to internal tissue. These catheters typically include a flexible catheter shaft and steering wires or other steering means for controlling the flexure of the catheter shaft. An example of a steerable catheter is shown by U.S. Pat. No. 5,199,950 to Schmitt, et al. U.S. Pat. No. 5,454,794 to Narcisco, et al. shows a steerable light-diffusing catheter for treating luminal surfaces with photodynamic therapy. A mechanism for steering a catheter is disclosed by U.S. Pat. No. 5,456,664 to Heinzelman, et al.
For certain applications, it has been found desirable by some practitioners to provide a steerable catheter with a locking steering mechanism. As the steering mechanism flexes the catheter shaft, the locking mechanism retains the shaft in the selected flexed position even after the steering dial is released. This can be accomplished, for example, by providing ridges or notches on the outer circumferential face of the steering dial, and providing a spring actuated pawl or other retaining element for engagement with the ridges or notches.
These locking steering mechanisms suffer the disadvantage that the steering mechanism locks only in discrete, spaced-apart positions, typically corresponding to the spaced ridges or notches on the outer circumferential face of the steering dial. Adjacent locking positions may be further apart than would be desirable to the practitioner. Thus, it has been found that a need exists for a fully adjustable steering lock mechanism that permits the user to lock the catheter shaft in any position within a continuous range.
Although locking steering mechanisms are often desirable, it is sometimes preferable to have a freewheeling steering mechanism that does not lock the shaft in position, but instead permits the catheter shaft to return to a generally straight configuration when the steering dial is released. Previously known locking steering mechanisms typically cannot convert into freewheeling mechanisms, which implicitly limits use to applications where freewheeling is not desired. It has therefore been discovered that needs exist for a steerable catheter having a steering mechanism that permits the practitioner to selectively engage or disengage a steering brake assembly. Further needs exist for a catheter whereby the user can choose to retain the shaft in a selected flexed position by locking the steering mechanism after releasing the steering dial, or alternatively, can allow freewheeling of the steering dial such that the catheter shaft returns to a generally straight configuration when the steering dial is released.
It is to the provision of a steerable catheter and steering brake assembly meeting these and other needs that the present invention is primarily directed.
Briefly described, in a preferred form, the present invention is a brake assembly for a steerable catheter that allows both dynamic locking and swapping between a locked mode of operation and an unlocked mode of operation. Dynamic locking enables very fine adjustment of the catheter shaft position, and locking of the shaft in an infinite number of positions through the entire range of motion of the catheter shaft. This advantageously frees the user from maintaining torque on the steering dial to maintain catheter tip positioning. Consequently, the user can concentrate on diagnosis, avoid hand fatigue, and use the hands for other tasks.
In addition to dynamic locking, preferred forms of the present invention allow swapping between a locked mode of operation and an unlocked mode of operation. Thus, a user can either lock the catheter shaft in a given position or allow freewheeling. During freewheeling, the catheter returns to a generally straight position after a user releases the steering dial. As a result, a user can more effectively redirect the direction of the catheter for further investigation. Thus, the invention also advantageously improves stability of catheter shaft positioning, which improves imaging and recording. Moreover, swapping between modes of operation results in a more multi-purpose catheter that can be used in both environments where locking catheters are needed as well as environments where non-locking catheters are needed.
In one preferred form, the invention is a brake assembly for dynamically locking a steerable catheter having a steering dial rotatable through a plurality of positions. The brake assembly comprises a brake shoe positioned for slidable movement between a locked position contacting the steering dial and an unlocked position not contacting the steering dial. At least one spring biases the brake shoe toward the locked position.
In another preferred form, the invention is a brake assembly for dynamically locking a steerable catheter having a steering dial rotatable through a plurality of positions. The brake assembly comprises a base assembly connected to the catheter and positioned proximate the steering dial. A spring-biased brake shoe is positioned in sliding relation to the base assembly and movable between a locked position engaging the steering dial and an unlocked position not engaging the steering dial. A toggle is pivotally connected to the base assembly and movable between a first position corresponding to the locked position of the brake shoe and a second position corresponding to the unlocked position of the brake shoe.
In another preferred form, the invention is a steerable catheter that comprises a catheter body, a flexible catheter shaft extending from the catheter body, and a steering dial rotationally mounted to the catheter body for manipulating the shaft. A brake assembly is also included. The brake assembly comprises a base assembly connected to the catheter body and positioned proximate the steering dial. A brake shoe is positioned in sliding relation to the base assembly and having a contact face slidably mounted to the catheter for selectively engaging and disengaging with the steering dial. The brake assembly further comprises at least one spring for biasing the contact face of the brake shoe against the steering dial.
In yet another preferred form, the invention is a steerable catheter comprising a housing, a flexible shaft extending from the housing, a steering dial for steering the shaft, and a brake assembly. The brake assembly preferably comprises a brake element frictionally engaged between the steering disc and the housing. In one embodiment of the invention, the brake element is a brake sleeve frictionally engaged between a socket in the housing and a boss on the steering dial. In another embodiment, the brake element is a brake shoe biased into frictional engagement with a face of the steering dial.
These and other features and advantages of preferred forms of the present invention are described herein with reference to the drawing figures.